Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint and openWorldHint, so safety profile is covered. The description adds the non-obvious cost signal '(1 credit)', which is genuinely useful. It does not disclose pagination, whether the calendar reflects private contributions, or what happens if the user does not exist.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two short, front-loaded sentences with no filler; the return shape leads and the credit cost trails. It is efficient, though the brevity borders on under-specification for a tool with three parameters.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description does carry the return-shape burden and does so at a high level (count per day, yearly total). It omits the url-versus-handle exclusivity, the year-override behavior, and error cases, leaving gaps for a tool that is otherwise simple.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so url, year, and handle are already documented, including the last-12-months default. The description adds nothing beyond the schema — it never mentions the url/handle choice or the year override, so the baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

Names a specific resource (a user's contribution calendar) and states the returned content: per-day counts plus a yearly total. The only GitHub siblings are trending developers/repositories, which are clearly different, so differentiation is implicit rather than argued.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no when-to-use guidance, no mention of alternatives, and no prerequisites (e.g., whether private contributions are included or whether a handle/url must resolve to a real account). Usage must be inferred entirely from the schema's parameter descriptions.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.